Dimerization process



' United States Patent ice j DIMERIZATION PROCESS N0 Drawing. Application December 6, 1954,

' Serial N0. 473,487

8 Claims. (Cl. 260-533) Thisinvention relates to a process for the preparation of dimerized products and more particularly, but not exclusively, to the dimerization of butadiene in the presence of sodium or potassium to produce a dialkali metal octadiene adduct. The invention also relates to the further reaction of this disodiooctadiene adduct (or potassium adduct) with carbon dioxide to produce dibasic acids or with other reagents to form corresponding difunctional products. i

The dimerization of butadiene in the presence of an active ether and metallic sodium or potassium has been reported previously (see Walker patent, U. S. 2,352,461). This prior method involves reacting the butadiene with the alkali metal in the presence of an active ether and simultaneously, min a subsequent step,r eacting the resultant product with carbon dioxide to form dibasic acids. In this process, the metal is employed in a solid form (in strips) and is pressed against a rotating scraper provided in the reaction vessel, the metal being abraded gradually during the progress of the reaction. This reaction is conducted at a temperature of between about 0 to 30 C. and upon carbonation produces a mixture of acids from which itis diflicult to isolate individual acids in any degree of purity. In the prior process, if the alkalimetal and butadiene were allowed to react to a substantial extent before admitting carbon dioxide to the reaction mixture, the final mixture of acids contained.

relatively large amounts of the higher dibasic acids. In addition, the use of this technique results in a considerable amount of polymerization of the butadiene, rather than the desired dimerization to form a disodio-octadiene adduct .(or potassium'adduct). Upon carbonation of this material, a complex mixture of many acids is produced rather than the desirable and valuable 10-carbon atom dibasic acids.

;It is accordingly an object of this invention to provide an improved dimerization process for conjugatedpolyenes,; such as butadiene. Another object is to provide a process which minimizes or avoids the formation of higher derivatives or polymeric materials. Another object is to provideja process which will selectively produce a dimerized aliphatic unsaturated hydrocarbon adduct with an alkali metal, such as sodium or potassium, which can be subsequently carbonated, or otherwise reacted, without the'prior problem of undue by-product formation. Another object is to provide a process which employs a highly active dispersed form of an alkali metal and is adapted to maintain it in highly reactive condition throughoutthe, course of the reaction. Other objects and advantages of this invention will become more apparent from the following description and appended claims.

We now have found that butadiene and other conjugated polyenes can be dimerized selectively, without the formation of any appreciable higher molecular weight by-products, such aspolymer, to form a low molecular weight aliphatic unsaturated hydrocarbon adduct with an alkali metal-in exceptionally high yields, of the order of 80 percent or higher. 0 This accomplished if the reaction is carried out, in the usual solvent system, using the alkali metal in highly dispersed form in the presence of a diaryl ketone, such as benzophenone. In contrast to the product obtained by using strips of sodium and carried out in the absence of the diaryl ketone, the reaction product of the present invention is almost entirely a dimerized adduct of the alkali metal and contains only very small quantities, if any, of higher molecular weight derivatives. Moreover, the low molecular weight adduct of this invention is relatively stable and can be reacted, even after relatively long periods of time, with other reactants, such as carbon dioxide, to give very useful and valuable relatively low molecular weight products.

In prior processes, as noted above, itwas necessary to use simultaneous addition of carbon dioxide to minimize somewhat the formation of higher molecular weight products. Using simultaneous addition, it was necessary to employ excess quantities of alkali metal due to deactivation ofthe alkali metal by the carbon dioxide. Thus, .better utilization of alkali metal can be achieved in the present process than with prior processes.

More particularly, the process of this invention for producing an aliphatic hydrocarbon adduct with an alkali metal, such as sodium or potassium, comprises adding a conjugated polyene, such asbutadiene, to finely dispersed alkali metal inareaction medium containing at least about 0.0001 percent of a diaryl ketone and above about 300 weight percent of a solvent, both based upon the weight of the alkali metal, at a temperature below about 50 C., the solvent being selected from the group consisting of ethers, acetals and tertiary amines.

In carrying outthis process, the diaryl ketone is added to the alkali metal prior to an appreciable reaction with the conjugated polyene. It can be added directly to the alkali metal, frequently dispersed in an inert solvent, or can be added to the active solvent, either before or after addition of the dispersed alkali metal.

In batch operation, the conjugated polyene should be added to the alkali metal, and shouldibe added over a sufficientperiod of timeto prevent a build-up of an excessive unreacted concentration, which condition favors the formation of polymer or other higher molecular weight compounds... This polyene addition can be either continuous or can be periodic. In any event, the total period of addition should generally be at least /2 hour and preferably atleast 2 hours.

The reaction can also be conducted in a continuous fashion in which event the polyene and alkali metal are continuously added in the preferred proportions. In using a continuous reaction, there is no tendency to build up an undue concentration of polyene and therefore the formation of high polymers is minimized or eliminated.

The polyenes useful for this invention should have between 4 and 16 carbon atoms. Typical examples are butadiene, pentadiene, hexadiene, octadiene, decadiene and pentadecadiene. Substituted dienes are also suitable for this invention. Typical examples of alkyl substituted dienes are isoprene, Z-ethyl butadiene, dimethyl butadiene, tertiary butyl-butadiene, Z-methyI-pentadiene, 3-methylpentadiene, 2-hexyl-pentadiene, Z-methyl-octadiene, 1,3- and 2-methyl-octadiene-2,4, 2-ethyl decadiene-1,3, 3-ethyl decadiene-2,4, cyclopentadiene, alloocimene, and the like.

Typical examples of aryl substituted dienes are l-phenyl butadiene, Z-phenyl butadiene, 1,4-diphenyl butadiene, naphthyl butadiene, and the like. Styrene also is suitable and for purposes of this invention is included as a conjugated polyene.

Total quantity of polyene added to the reaction medium is normally not appreciably greater than stoichiometric quantities, based upon the alkali metal, i. e., 1 mole of polyene per mole of alkali metal, and generally is employed in a molar ratio of not less than 0.4:1. Prefero use a leas one pa t o d ue t b o ume n t pa t of Polyene.

The princ pal alkali metals s i a le o this i ent n are sodium and pot ium- While th othe a ka met l are usefu hey ar 'generally less esi able fo ec nom reasons. In addition to the use of the pure metals noted, alloys or mixtures of these metals can e mploy d wi other alkali metals or with alkaline eart metals.

The alkali metal must be used as a fine dispersion have ing an average particle size normally not more than 50 microns. It is preferred to use an alkali metal having an average particlesize below about '15 microns. In general, the finestparticle size obtainable produces the best results.

The alkali metal dispersion is normally made in an inert organic solvent such as iso-octane, heptane, decane, purified kerosene, other non-reactive petroleum fractions, di n-butyl ether or similar materials. In some cases the ether, acetal or amine solvent can be used advantageously as the dispersion medium. When employed, the quantity of dispersion medium is not critical and can range from about equal quantities based upon the alkali metal to a quantity equal to the weight of the solvent employed. The

dispersion can be made by any suitable well-known method. It is generally preferred to use a high speed agitator and a small quantity of a dispersing agent, 'suchas oleic acid, linoleic acid, dilinoleic acid, carbon black, etc. Normally the dispersion is made at an elevated temperature and is thereafter allowed to cool to room temperature or lowerl prior to use in the process of this invention.

The diaryl ketones useful in the present invention are compounds in which the aryl groups are phenyl, naphthyl, biphenyl, or any of the higher condensed or non-condensed polynuclear radicals or any combination of these radicals. Typical examples of diaromatic ketones are benzophenone, phenyl naphthyl ketone, dinaphthyl ketone, phenyl biphenyl ketone, dibiphenyl ketone, phenyl terphenyl ketone, biphenyl naphthyl ketone, diterphenyl ketone and cyclic ketones, such as fiuorenone. V

In general, the concentration of the diaromatic ketone should be controlled to prevent the formation of byproducts. If the ketone is used in excess, it not only wastes quantities of the reactants but the by-products tend to contaminate the product. It is most frequently eonvenient to control the qnantity of diaromatic' ketone needed in the process by'addin'g suflicient quantities to the reaction medium, prior to the addition of polyenes, to give a reaction mixture having a color characteristic of the alkali metal ketyl of the particular ketone used, such as blue or purple with benz'ophenone. This color normally is dissipated after beginning the addition of the butadine or other polyenes to the "reaction mixture. In general, this concentration is not less than about 0.0001 nor more than weight percent, based upon the weight of the alkali metal, but a more preferred range is between 0.001 and about 1.0 weight percent. Excessive quantities, as noted above, reducethe yield ofthe desired adduct through formation of by-products.

Th ol en it bl fo u n he Pre n nvention s Poin o t ab a e t th r aootals and ter i m s- A e er d group of o hers o u e in e re en en o o u o ot i hatic mo and o otho s- The preferred monoethers have a CH O' group and have an oxygenzcarbon ratio not less than l :4, 7 Typical x mp e o t o e Pr e red. monoe he s' a? tio r he m thy hyl he m thy soorop o her. me h l. n-p op l o r o mixt es o ho ers h abo e the s a so fan' s' m ed w h'h ro' a ben s l ents f desired. i

The preferred polyethers are ethylene glycol diethers,

sas s met t l. methyl eth l... h l ethyl. meth l butyl, ethyl but yl, butyl butyl, butyl lauryl; diethylefie glycol ethers, such a methyl methyl, ethyl ethyl, ethyl butyl and butyl lauryl; trimethylene glycol ethers, such as dimethyl, diethyl, methyl ethyl, etc.; glycerol ethers, such as trimethyl, dimethyl ethyl, diethyl methyl, etc.; and cyclic ethers, such as dioxane, tetrahydrofuran, methyl glycerol formal, dimethylene pentaerythrite.

A wide variety of acetals also can be used in the present invention. Typical examples of suitable acetals are methylal, l,1-din1ethoxy ethane, 1,-1,- dimeth9Xy propane, 1,1-dimethoxy butane, glycol formal, methyl glycerol formal, etc. The preferred acetals are methylal, 'glycol formal and methyl glycerol formal.

A wide varietyrof tertiaryamines are suitable for this invention including both aliphatic and aromatic amines. The preferred tertiary amines for use in this invention are methy am e hyl ethyl am e. tet a methy m y ne diamin n nvl mo pholin The active solvent should have ahigh degree of purity to avoid contamination of the alkali metal surface. The amount of active solvent employed in the reaction mixr: ture can be varied considerably without departing from the scope of the invention. The amount used generally will depend on the particular reactants and solvent used. In general, the use of from 100 to 2,000 cc. of solvent per gram mole of sodium, i. e. not less than 30.0 percent'by weight of the alkali metal is recommended as a suitable reaction dilution. When a diluent, e. g. an inert hydrocarbon dispersant for the alkali metal, is used along with the active solvent, sufiicient active solvent should be present to have an active promoting effect upon the reaction. In general, it is preferred to use a reaction medium which contains a weight of active solvent at least as great as the weight of any co-present diluent.

The temperature of the reaction is preferably maintained below-about 50 C. but above the melting point of the solvent system. With most reaction media, it is preferred to maintain the temperature below about 0- 6. Highly desirable reactions can be obtained as low as C.

The reaction mixture throughout the course of the reactionshould be agitated vigorously to insure complete mixing of the polyene with the dispersed alkali metal mixture and to facilitate heat transfer in the system. i I

The process can be conducted either in a batch or continuous manner, When carried out continuously," it is preferred to employ a tube type reactor. In the'latte'r case, the polyene and sodium dispersion in the active ether can be fed continuously in the desired proportions to the inlet end of the tube-type reactor.

The reaction should be conducted in an inert atmosphere to exclude oxygen, moisture, carbon dioxide, and other impurities which would be reactive toward the alkali metal adduct, the reaction preferably being carried out employing a dry nitrogen atmosphere or otherinert gas.

In addition to carbonationofthe alkali metasl adduct, the adduct can be reacted with many other Grignard type reactants, having carbonyl, thionyl, and nitrile groups to form highly desirable products. Typical examples of such reactants are sulfur dioxide, benzene sulfonyl chloride, thionyl chloride, formaldehyde, acetone, ethylene oxide, propylene oxide, acetonitrile, propionitrile, and the like. For example, the organo alkali metal adduct can be reacted in typical Grignard type reactions with sulfur dioxide to form disulfinic acids with'formaldehyde or epoxides to give diols, with cyanogen chloride to give .cyclodienyl {compounds to efiect transmetalation .and--.the .metalated product; can thereafter be reacted with any i of thejfirignardrtype.reactants,,noted above.

1"he;-.temperature:of {the subsequent :reaction is generally not critical. However, with certain of the reactions discussed such as. carbonation, .it {is necessary. to :conduct the reaction in the cold, below about 0 C. and preferably The g following examples illustrate our invention but are not intended to in any way limit the scopethereof. 'In

these examplesgall parts are by -weight.

Example I Dimethylether,.(149.-parts) was .charged'to areaction 1 vessel maintained'gbelow -50 jC. and equipped with .a stirrer, alreflux con'denser a thermometer and a gas inlet tube adapted to exten'dbelow'the surface of'the .reaction mixture. The dimethyl ether employed was previously purified ,by stirring with. sufficient --$1llllltill$ of sodium and benzophenone to form the'blue'lketyl. The ether' then was distilled "from this mixture. Sodium (12.5

:parts.) ,tpreviously .dispersed .in purified akerosene and .having an average particlesizeof about :.8 microns, .was added :toitheether undenan atmosphereofdr-y nitrogen. .Benzophenone (0.019 part) was.added. .to.this mixture and produced a blue color. "The temperature 'of the system then was raised-to-30--C. A-total-of 2212 parts of butadiene,

about forty-five minutes after completion of addition of the butadiene.

Following completion of the above dimerization reaction, 80 parts of dry isooctane were added to the reaction mixture. The mixture was thereafter carbonated by pouring the same onto a large excess of crushed solid carbon dioxide. Following vaporization of the excess carbon dioxide, 100 parts of water were added to the reaction mixture to destroy the unreacted sodium. The resulting reaction mixture then was permitted to separate into an aqueous solution of the product salts (unsaturated carbon atom dibasic acid salts) and a hydrocarbon fraction.

The product acids were thereafter recovered from the aqueous phase by acidification and extraction with ether. These unsaturated acids were thereafter saturated by a conventional hydrogenation process at room temperature in ether solution, using a platinum oxide catalyst.

The total yield of crude acid was 33.7 parts having an average neutralization equivalent of 104 (corresponding to the theoretical of 101 for IO-carbon dibasic acids). This acid mixture, upon separation, contained about percent sebacic acid; 52 percent Z-ethyl suberic acid; 10 percent 3-ethyl suberic acid; and 2,2-diethyl adipic acid; and the remainder contained principally valeric and pelargonic acids.

The hydrocarbon layer was distilled, obtaining only 2.2 parts of polymer.

Example II hyde is added continuously over a one-hour period, using agitation throughout the reaction. The decadienediol product mixture is recovered by flashing the solvent at essentially atmospheric pressure, reacting the remaining sodium with an excess of ethyl alcohol, and separating by fractional distillation of the product.

fix mp a l Example] is repeate'd exeept' 'thatthe ma as-r acted with e'thylene oxide'= to= produce dodeca'dienediols. "In'this exarnple, ethylene oxidcwapor (2'5 pairtsL-ftlilute'davtlith tlr-y nitrogen, is passed, -ove'r a-period of one "hour, into the 'reaction mixturei maintained at 30 C. 'I he solvent isi'listilledandtthe sodiumareacted withan excess ofiethyl alcohol. 9 The mixture is thereafterfractionatedtto obtain fithe'diol product. ExamplellV Example I was repeated :except tthat the ladduct was reacted with toluene to effect transmetalationaandthe z-b'enzyl zsodium :so stormed awas thereafter areacted with carbon adioxide .to form :phenyl acetic acid. in this "ex- :ample, the sodium initially was dispersed :;in 18.5 :parts of ztoluene. -Followingzthe;formation of :the disodioocta- -.=diene adduct, an additional -88 iparts of toluene were added. This mixture :then was :heated to distill --.th e .methyl ether solventand the meactiommixturetwas stirred :at 2100-":105 :C. :for ?.two hours. The ireac'tiontmixture :thereafterawascooled'to 0'=C.:and poured on solid'scarbon -,dioxide. -.61parts of .phenyl acetic acid were obtained ;-from tthe aqueous .:fraction. The rhydrocarbon *fraction was -rlistilled, tleaving a residue 10f only 1.0 part of ,;poly- Example V commencing addition of butadiene and later changed to brown. During the subsequent post reaction stirring, the reaction mixture turned green.

The subsequent reaction with carbon dioxide corresponded to Example I. The product (10.5 parts) had an average neutralization equivalent of 101, corresponding to theoretical for 10-carbon dibasic acids. The product distribution was similar to Example I. Only 1.5 parts of polymer was obtained from the hydrocarbon fraction.

Example VI Example I was repeated except that a total of 13.5 parts of butadiene were reacted over a period of 2 to 3 hours, using a continuous addition. 20.9 parts of product were obtained having a neutralization equivalent of 103 and having essentially the same product distribution of Example I. The hydrocarbon phase was distilled, giving only 1.2 parts of polymer.

Example VII Example I is repeated except that isoprene is substituted for butadiene using 28 parts of the isoprene and 12.5 parts of sodium. The product is obtained in good yield and consists of C12 dicarboxylic acids.

Example VIII Example I is repeated except that a mixture of methyl- 1,3-pentadienes is substituted for butadiene using 34 parts of the pcntadiene and 12.4 parts of sodium. The product is obtained in good yields and consists of C14 dicarboxylic acids.

The above examples have been repeated using methylal, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, trimethyl amine at -30 C. and similar results were obtained.

When the above examples are repeated using other alkali metals, such as potassium and lithium or alloysand mixtures of alkali metals and alkaline earth metals such as sodium-potassium, sodium-calcium and the like, generally the sameresults are obtained,

The products of this process have a wide variety of .uses as such and these products also can be employed as intermediates in the preparation of many other useful compounds. In particular, the dibasic acids, esters, ketones and other products produced by this invention are very valuable in the manufacture of condensation polymers, such as the nylon type, which are useful in the manufacture of fibers, films, and molded articles. These products can also be used as plasticizers for resins, synthetic lubricants and the like.

We claim:

1. The process. for dimerization of a conjugated hydrocarbon polyene in the presence of an alkali metal to produce a dialkali metal polyene adduct comprising adding a conjugated polyene having between 4 and 16 carbon atoms to a reaction medium maintained at a temperature below about 50 C. containing finely dispersed alkali metal having a particle size not greater than 50 microns, between about 0.0001 and 10 percent of a diaryl ketone and at least 300 percent of an aliphatic solvent selected from the group consisting of ethers, acetals and tertiary amines, both percentages being based upon the weight of said alkali metal, said polyene being employed in a total quantity not exceeding about 1 mole per mole of alkali metal.

2. The process of claim 1 wherein the reaction mixture so-formed,including said diaryl ketone, is thereafter treated with a Grignard reactant selected from the group consisting of carbonyl, thionyl and nitrile compounds.

3. The process of claim 1 wherein the polyene is a diene. 7

4. The proce ss of claim 1 wherein the polyene is butadiene.

5. The process of claim 1 wherein the polyene to alkali metal molar' ratio is from about 0.7:1 to about 0.95: 1.

6. The process of claim 1 wherein the diaryl ketone is employed in a concentration of between about 0.001 and about 1.0 weight percent based upon the weight of the alkali metal.

,7. The, process of claim 1 wherein the diaryl ketone is benzophenone and the alkali metal is sodium.

8. The process of claim 2 wherein the Grignard reactant is carbon dioxide.

References Cited in the file of this patent UNITED STATES PATENTS 1,832,450 Ebert et al. Nov. 17, 1931 2,352,461 Walker July 27, 1944 2,716,662 Cohen et al. Aug. 30, 1955 FOREIGN PATENTS 1,093,096' France Nov. 17, 1954 

1. THE PROCESS FOR DIMERIZATION OF A CONJUGATED HYDROCARBON POLYENE IN THE PRESENCE OF AN ALKALI METAL TO PRODUCE A DIALKALI METAL POLYENE ADDUCT COMPRISING ADDING A CONJUGATED POLYENE HAVING BETWEEN 4 TO 16 CARBON ATOMS TO A REACTION MEDIUM MAINTAINED AT A TEMPERATURE BELOW ABOUT 50* C. CONTAINING FINELY DISPERSED ALKALI METAL HAVING A PARTICLE SIZE NOT GREATER THAN 50 MICRONS, BETWEEN ABOUT 0.0001 AND 10 PERCENT OF A DIARYL KETONE AND AT LEAST 30 PERCENT OF AN ALIPHATIC SOLVENT SELECTED FROM THE GROUP CONSISTING ETHERS, ACETALS AND TERTIARY AMINES, BOTH PERCENTAGES BEING BASED UPON THE WEIGHT OF SAID ALKALI METAL, SAID POLYENE BEING EMPLOYED IN A TOTAL QUANTITY NOT EXCEEDING ABOUT 1 MOLR PER MOLE OF ALKALI METAL.
 2. THE PROCESS OF CLAIM 1 WHEREIN THE REACTION MIXTURE SO-FORMED, INCLUDING SAID DIARYL KETONE, IS THEREAFTER TREATED WITH A GRINGARD REACTANT SELECTED FROM THE GROUP CONSISTING OF CARBONYL, THIONYL AND NITRILE COMPOUNDS. 